The overall, long-range objective of the project concerns a systematic description of psychophysical characteristics and underlying physiological processes of biological sensory systems. The current emphasis is on the auditory system. Nevertheless, some experiments and theoretical analyses currently in progress and scheduled for the next year of the project invade the tactile and visual systems. These incursions are made to test the generality of observed phenomena and investigate heterosensory interactions. More specifically, the research deals with direct scaling of sensory magnitudes and with their additivity, with central masking and its psychophysiological theory, with measurement of intensity characteristics of sensory receptors and their biophysical theory, with adaptation and saturation phenomena measured in the inner hair cells, cochlear-nerve fibers, and cochlear-nucleus units, with the possible interaction between cochlear inner and outer hair cells, and with the theory of sound transmission in the inner and middle ear. Perhaps the greatest weight should be attached to the scaling of sensory magnitudes, without determination of suprathreshold sensory characteristics is not possible, and the experimental and theoretical work on receptor intensity characteristics, which aims at the improvement and further validation of a mathematical formulation that has been demonstrated to hold for a large number of receptor types. The planned recording from cochlear inner hair cells, if successful, would clarify a host of questions on cochlear neurosensory processes.